1. Field of the Invention
This invention relates to a rotational direction detecting apparatus for detecting a rotational direction of a rotated member rotated by a motor, and further to a rotational direction detecting apparatus capable of detecting a rotational speed of the rotated member.
2. Description of the Related Art
Conventionally, a mechanism part (hereinafter called xe2x80x9ca rotating mechanism partxe2x80x9d) for rotating a rotated member by a motor has been applied to various apparatus. For example, a CD player or a DVD apparatus provides a rotating mechanism part for rotating a turntable (equivalent to the rotated member) on which a CD or a DVD (a disk medium) is placed, and the disk medium is rotated by rotating this turntable.
Also, the apparatus providing the rotating mechanism part is provided with a mechanism part (a rotational direction detecting apparatus described by the invention) for detecting a rotational direction or a rotational speed of the rotated member.
For example, there was a rotational direction detecting apparatus disclosed in JP-A-4-50771. In this rotational direction detecting apparatus, a disk in which slits with different sizes respectively are formed in four places on concentric circles is mounted in a rotating shaft of a motor. The rotated member is mounted in the rotating shaft of this motor. The slits are in a position in which one of the edges is divided into four equal portions radially with respect to the center of the disk. Also, ratios of the lengths of the four slits are 1:2:3:4 on the concentric circles and the four slits are formed clockwise in this order. Also, a photo interrupter for applying light from one side with the disk sandwiched and detecting the light passing through the slits in the other side is provided.
In this rotational direction detecting apparatus, a pulse width detected by the photo interrupter becomes long gradually in the case of rotating at constant speed clockwise and the pulse width detected by the photo interrupter becomes short gradually in the case of rotating at constant speed counterclockwise in reverse, so that a rotational direction is determined by detecting a change in this pulse width.
Also, a rotational speed is calculated from time taken from fall timing of an arbitrary pulse detected by the photo interrupter to fall timing of the next pulse in the case of rotating at constant speed clockwise, and is calculated from time taken from rise timing of an arbitrary pulse detected by the photo interrupter to rise timing of the next pulse in the case of rotating at constant speed counterclockwise.
However, the rotational direction detecting apparatus cannot determine the rotational direction unless it respectively detects the pulse widths of the light passing through the four slits by the photo interrupter. Also, unless the rotational direction is determined, the rotational speed cannot be calculated. Here, there was a problem that time taken to rotate the disk once is necessary to respectively detect the pulse widths of the light passing through the four slits by the photo interrupter and time taken to detect the rotational direction is long.
An object of the invention is to provide a rotational direction detecting apparatus for reducing time necessary to detect a rotational direction of-a rotated member.
Another object of the invention is to provide a rotational direction detecting apparatus for achieving cost cutting of a main body by simplifying processing performed in detection of a rotational direction of a rotated member.
In order to solve the problems, a rotational direction detecting apparatus of the invention comprises the following configurations.
(1) There are provided rotation means for rotating a rotating disk on which a pattern for alternately repeating reflection and non-reflection or transmission and non-transmission of light is formed along with a rotated member, detection means for applying light to the rotating disk rotated by the rotation means and detecting a pulse waveform by its reflected light or transmitted light, and rotational direction determination means for determining a rotational direction of the rotated member based on the pulse waveform detected by the detection means, and the rotating disk is a rotating disk on which plural sets of patterns in which pulse widths of pulses detected at the time of normal rotation increase or decrease continuously in three steps or more are formed, and the rotational direction determination means determines a rotational direction of the rotating disk from a change in pulse widths or pulse intervals of continuous pulses.
In this configuration, the rotation means rotates the: rotating disk along with the rotated member. The rotating disk is mounted in, for example, a rotating shaft of a motor directly or through a gear. The rotated member and the rotating disk are rotated in the same direction at the same rotational speed. Therefore, a rotational direction and a rotational speed of the rotated member can be detected by detecting a rotational direction and a rotational speed of the rotating disk.
Since the rotating disk is a rotating disk on which plural sets of patterns in which pulse widths (or pulse intervals) of pulses detected at the time of normal rotation increase (or decrease) continuously in three steps or more are formed, by detecting four continuous pulses (or pulse intervals), it can be determined whether the pulse widths (or pulse intervals) have changed in an increase direction or a decrease direction and as a result, a rotational direction can be determined. When the pulse widths (or pulse intervals) have changed in the increase direction, there is normal rotation (reverse rotation in the case that decreasing patterns are formed) and in reverse, when the pulse widths (or pulse intervals) have changed in the decrease direction, there is reverse rotation (normal rotation in the case that decreasing patterns are formed).
Since plural sets of the patterns are formed on the rotating disk, four continuous pulses (or pulse intervals) can be detected during time shorter than time for which the rotating disk rotates once. Therefore, time necessary to acquire information (pulse widths (or pulse intervals) of four pulses) necessary to determine a rotational direction can be reduced, so that a reduction in time taken to determine the rotational direction can be achieved.
Incidentally, five or more continuous pulses (or pulse intervals) may be detected in the case of determining the rotational direction, but when the number of pulses to be detected is increased, time necessary to detect the rotational direction becomes long by the increased number, so that the number of pulses to be detected is preferably set to four.
(2) The rotating disk is a rotating disk on which plural sets of patterns in which pulse widths or pulse intervals of pulses detected at the time of normal rotation increase or decrease continuously in three steps are formed, and there is provided rotational speed calculation means for calculating a rotational speed of the rotating disk from the minimum pulse width or pulse interval detected.
In this configuration, all the pulses obtained with respect to one set of the pattern formed on the rotating disk can be detected. Here, sizes of the pattern in which the pulse width or pulse interval becomes minimum, the pattern in which it becomes the maximum and further the pattern in which it becomes a middle size are known. Therefore, a rotational speed of the rotating disk can be calculated from the pulse width or pulse interval of any pulse and a size of the pattern in which its pulse width or pulse interval is obtained.
(3) The pattern formed on the rotating disk is a pattern in which the pulse widths or the pulse intervals become constant at the time of rotation at constant speed and there is provided rotational speed calculation means for calculating a rotational speed of the rotating disk from said pattern.
In this configuration, the pulse widths or the pulse intervals obtained at the time of rotating the rotating disk at constant speed are constant. That is, a size of non-reflection (or pattern of non-transmission) formed on the rotating disk is the same. This size is known, so that a rotational speed of the rotating disk can be calculated by detecting the pulse widths or the pulse intervals.
(4) There are provided rotation means for rotating a rotating disk on which a pattern for alternately repeating reflection and non-reflection or transmission and non-transmission of light is formed along with a rotated member, detection means for applying light to the rotating disk rotated by the rotation means and detecting a pulse waveform by its reflected light or transmitted light, and rotational direction determination means for determining a rotational direction of the rotated member based on the pulse waveform detected by the detection means and the rotating disk is a rotating disk on which plural sets of patterns in which rise intervals or fall intervals of continuous pulses detected at the time of normal rotation increase or decrease continuously in three steps or more are formed, and the rotational direction determination means determines a rotational direction of the rotating disk from a change in the rise intervals or the fall intervals of continuous pulses.
In this configuration, the rotation means rotates the rotating disk along with the rotated member in a manner similar to (1) described above. The rotating disk is mounted in, for example, a rotating shaft of a motor directly or through a gear. The rotated member and the rotating disk are rotated in the same direction at the same rotational speed. Therefore, a rotational direction and a rotational speed of the rotated member can be detected by detecting a rotational direction and a rotational speed of the rotating disk.
Since the rotating disk is a rotating disk on which plural sets of patterns in which rise intervals or fall intervals of continuous pulses detected at the time of normal rotation increase (or decrease) continuously in three steps or more are formed, four rise intervals or fall intervals of continuous pulses can be obtained by detecting rises or falls of five continuous pulses. It can be determined whether the rise intervals or fall intervals have changed in an increase direction or a decrease direction from the four rise intervals or fall intervals and as a result, a rotational direction can be determined.
Here, the rises or falls of five continuous pulses can be detected during time shorter than time for which the rotating disk rotates once in a manner similar to (1) described above. Therefore, a reduction in time necessary to detect the rotational direction can be achieved.
Also, since it is unnecessary to detect the falls or rises of pulses, processing necessary to determine the rotational direction is reduced by the amount, and a further reduction in time necessary to determine the rotational direction can be achieved. Further, a configuration of an apparatus body can be simplified, so that cost cutting of the apparatus body can be achieved.
Incidentally, rises or falls of six or more continuous pulses may be detected in the case of determining the rotational direction, but when the number of detections is increased, time necessary for this detection becomes long, so that it is preferable to detect rises or falls of five continuous pulses and determine the rotational direction.
(5) The rotating disk is a rotating disk on which plural sets of patterns in which rise intervals or fall intervals of continuous pulses detected at the time of normal rotation increase or decrease continuously in three steps are formed, and there is provided rotational speed calculation means for calculating a rotational speed of the rotating disk from the minimum rise interval or fall interval detected.
In this configuration, all the rise intervals or fall intervals obtained with respect to one set of the pattern formed on the rotating disk can be detected. Here, sizes of the pattern in which the rise interval or fall interval becomes minimum, the pattern in which it becomes maximum and further the pattern in which it becomes a middle size are known. Therefore, a rotational speed of the rotating disk can be calculated from any rise interval or fall interval and a size of the pattern in which its rise interval or fall interval is obtained.